(1) | ||
size_type size() const; | (until C++11) | |
size_type size() const noexcept; | (since C++11) (until C++20) | |
constexpr size_type size() const noexcept; | (since C++20) | |
(2) | ||
size_type length() const; | (until C++11) | |
size_type length() const noexcept; | (since C++11) (until C++20) | |
constexpr size_type length() const noexcept; | (since C++20) |
Returns the number of CharT
elements in the string, i.e. std::distance(begin(), end())
.
(none).
The number of CharT
elements in the string.
Unspecified. | (until C++11) |
Constant. | (since C++11) |
For std::string
, the elements are bytes (objects of type char), which are not the same as characters if a multibyte encoding such as UTF-8 is used.
#include <cassert> #include <iterator> #include <string> int main() { std::string s("Exemplar"); assert(8 == s.size()); assert(s.size() == s.length()); assert(s.size() == static_cast<std::string::size_type>( std::distance(s.begin(), s.end()))); std::u32string a(U"ハロー・ワールド"); // 8 code points assert(8 == a.size()); // 8 code units in UTF-32 std::u16string b(u"ハロー・ワールド"); // 8 code points assert(8 == b.size()); // 8 code units in UTF-16 std::string c("ハロー・ワールド"); // 8 code points assert(24 == c.size()); // 24 code units in UTF-8 #if __cplusplus >= 202002 std::u8string d(u8"ハロー・ワールド"); // 8 code points assert(24 == d.size()); // 24 code units in UTF-8 #endif }
checks whether the string is empty (public member function) |
|
returns the maximum number of characters (public member function) |
|
(C++17) | returns the number of characters (public member function of std::basic_string_view<CharT,Traits> ) |
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